Continue fighting pthreads.

Clean up thread library a bit too.

src/libthread/sleep.c

@@ -0,0 +1,38 @@
+#include "threadimpl.h"
+
+int _threadhighnrendez;
+int _threadnrendez;
+
+void
+_threadsleep(_Procrend *r)
+{
+	Thread *t;
+
+	t = _threadgetproc()->thread;
+	r->arg = t;
+	t->nextstate = Rendezvous;
+	t->asleep = 1;
+	unlock(r->l);
+	_sched();
+	t->asleep = 0;
+	lock(r->l);
+}
+
+void
+_threadwakeup(_Procrend *r)
+{
+	Thread *t;
+
+	t = r->arg;
+	while(t->state == Running)
+		sleep(0);
+	lock(&t->proc->lock);
+	if(t->state == Dead){
+		unlock(&t->proc->lock);
+		return;
+	}
+	assert(t->state == Rendezvous && t->asleep);
+	t->state = Ready;
+	_threadready(t);
+	unlock(&t->proc->lock);
+}